1. Field of the Invention
The present invention concerns a method for adjusting the distance between two elements, at least one of which is mobile. It also concerns a device permitting this adjustment, this device comprising an elastic link with an exponentially progressive resistivity to elongation, depending on the tensile force applied to it. The invention also concerns a swimming harness applying this method and this device.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
It is common practice to use elastic cables or cords composed of several rubber threads placed side by side under a sheath, for various uses such as, for example, fastening of packages or luggage on a support, launching of gliders, braking of airplanes at landing [arrestor wires on aircraft carriers], etc.
The elastic threads of the bundle constituting these cables or multi-stranded cords are all of the same length and are fastened at their opposing ends to a buckle or some other fastening device, so that their resistance to elongation is uniform up to the point where they approach their stretch limit.
In certain applications, this resistance to uniform stretch constitutes a drawback. Such a drawback is experienced, in particular, when the elastic band is used as a means for retaining a swimmer swimming in place, for instance in a pool of small dimensions (see U.S. Pat. No. 5,083,522 and DE-197 41 309). In this situation, the swimmer is wearing a harness and is tethered to a rim of the pool or to a fixed point near this rim, by means of a fully (DE-197 41 309) or partially (U.S. Pat. No. 5,083,522) elastic tether which allows to keep him at a distance from the opposite rim of the pool, for example in the middle part or essentially in the middle part of the pool, so that he may swim without having to change direction incessantly for the desired duration.
In this case, the drawback resulting from the uniform elongation of the elastic strands forming the retaining straps, or the elastic portion of these, is that one is obliged to provide a set of several straps with different stretch capabilities, so that each swimmer will be able to select a specific strap that is suitable to his age, or to his level of swimming, or to his physical strength.
As a matter of fact, an elastic strap with a low capacity of elastic elongation, i.e., of high resistance to stretching, will not permit a young swimmer or a beginner to move forward, so that they will not experience the sensation of a normal swim, whereas an elastic strap with a greater degree of stretch, i.e., with low resistance to stretching, will not keep a good swimmer in the middle part of the pool.
One is also familiar (DE-25 02 925) with energy-absorbing devices applicable to the safety belts in automobiles and consisting of a number of elastic belts of different lengths which are fastened at two fixed points in the interior of the vehicles. These energy-absorbing devices operate on the principle of a system featuring characteristics of progressive elongation depending on the severity of the shock, but they are not designed to adjust a variable distance between two points.